The present invention relates to a single lever control with throttle and forward-reverse clutch functions for marine power plants, comprising a shaft coupled to an operating lever and rotatably journalled in a supporting element, a motion-transmitting mechanism acting between the shaft and the throttle means, and electrical switch means actuated by the turning of the shaft for controlling the electrical servo means governing the clutch function.
By far the most common known type of single lever control transmits the lever movement entirely mechanically via a first so-called push-pull or Bowden cable to the engine throttle and via a second push-pull cable to the engine clutch means on the reversable transmission. During the initial lever movement from the neutral position to drive engagement, either forward or backward, a certain delay in the throttle function is always required, so that the forward or reverse gear will have time to be engaged completely before the throttle is opened to any appreciable degree. A number of different types of lost motion mechanism has been developed to provide this delay, most of which are based on the principle of displacing the travel cable jacket as much as the control wire during initial movement of the control lever. The known lost motion mechanisms are linkage systems, cam curve systems and combinations thereof, and are relatively complicated as well as being subject to significant wear. The greater the distance from the operator seat or control console to the engine, the greater the resistance will be in the control cables and this leads to increased stresses and increased wear in the control components. When the control console is located on a flybridge, unavoidable bends contribute to increased resistance in the system and thus the maximal operating force required. The problem is particularly pronounced in the forward-reverse clutch function, since the required operating force to engage forward or reverse is significantly greater than the engine throttle function. This means that the lever movement, i.e. the mechanical advantage in the control, must be adapted to the required manual operating force in such a manner that the operator does not experience the shifting movement as being too hard. This limits the possibility of dimensioning the control for a short lever movement for engaging forward or reverse, which would have been desirable to be able to shorten the lost motion of the throttle function. A short lost motion makes it possible to simplify the lost motion mechanism.
In order to avoid the problem of wear in the components of the clutch mechanism, it has previously been suggested to have the engagement and disengagement be performed with the aid of a servo motor to thereby reduce the clutch control mechanisms in the single lever control to a pair of electrical switches and a cam element interacting therewith. Such a control, which is shown in SE-A-391 903, has the electrical switches with accompanying clutch means arranged in such a manner that the lever angle between the neutral position and either engaged position is relatively great, almost 45.degree.. The throttle function comprises a cam follower and a cam curve arrangement to provide the relatively long lost movement required for the delay in opening the throttle.
The purpose of the present invention is generally, starting from the possibilities provided by electrical servo control of the forward-reverse clutch function, to achieve a single lever control of the type described by way of introduction, which is of simpler construction than previously known single lever controls at the same time as purely functional improvements are achievable in relation thereto.
This is achieved according to the invention by virtue of the fact that the motion-transferring mechanism comprises a link arm having, spaced from the centre of the shaft, a first pivot-joint to an element attached to the shaft and a second pivot joint to a lever element for transmitting motion to the throttle means, the pivot points of the link arm being arranged so that their centres lie on opposite sides of the shaft and on a straight line through the axis of rotation of the shaft, when the operating lever is in a neutral position wherein switch means put the servo motor in a neutral position.
The control according to the invention has no real lost motion mechanism, but rather uses instead a "progressive" motion transmission ratio between the control lever and a lever to which an operating cable is connected. For movement of the control lever within a range of 15.degree. from the neutral position, the movement of the cable lever will be negligible and by placing the electrical switch means so that they are turned on or off within this range, forward or reverse will be engaged without opening the throttle. When the control lever is then moved further, the throttle opening will be progressively greater providing smooth acceleration to full throttle opening. This avoids the disadvantage of most known lost motion mechanisms which have means which achieve, after engagement, a sudden locking of the cable jacket, which results in a rapidly increasing throttle opening.